Field of the Invention
Embodiments of the present invention relate generally to rendering graphics images and more specifically to computerized image rendering with per-frame buffer scene segmentation.
Description of the Related Art
High-quality graphics rendering systems are conventionally used to generate highly refined images, such as photorealistic images, from mathematical models of three-dimensional (3D) scenes. Unlike real time graphics rendering systems, which typically render sixty or more images per second, many high-quality graphics rendering systems commonly require several minutes to over a day to render a single image. Because the goal of high-quality rendering systems is to render images to the highest technically feasible standards, iterations of fine-tuning operations are frequently applied to each image before a final image is produced. Fine-tuning iterations are typically conducted by a user who may visually examine an image before accepting the image or proceeding with an additional fine-tuning iteration.
To minimize the enormous computational time and effort associated with fully rendering a high-quality image in conjunction with performing numerous fine-tuning iterations on the image, the overall rendering process is partitioned into a rendering phase and a compositing phase, wherein the fine-tuning iterations may be substantially performed in the compositing phase. In this approach, individual scene elements (objects within a virtual environment) or groups of scene elements may be independently rendered as scene segments that are stored within corresponding frame buffers. Computationally efficient compositing operations are then used to combine the scene segments to generate a final image. Contributions from individual segments may be adjusted in the compositing phase to perform fine-tuning operations without repeating a time consuming rendering phase. For example, if a specular highlight of a scene element is rendered into a separate segment, the intensity of the specular highlight may be adjusted independently via one or more compositing iterations to fine-tune the contribution of the specular highlight without re-rendering the image. Because the rendering phase comprises a significant majority of the overall computation time, and the compositing phase requires a relatively small amount of computation time, excellent overall efficiency is achieved with this approach, even when multiple compositing iterations are needed.
One key aspect to this partitioned approach involves determining how a scene should be decomposed into segments, according to individual scene elements or groups of scene elements. Typically, a user may select one or more scene elements to be rendered separately from the other scene elements, which are excluded from rendering. The scene elements of the decomposed scene are then rendered in separate rendering passes to generate each respective scene segment.
This approach has at least two significant drawbacks. The first drawback is that in a given rendering pass, excluded scene elements do not contribute to a rendered segment of selected scene elements, resulting in degradation of both image quality and realism. For example, a selected scene element that is supposed to be reflective will not actually include a reflection of a nearby scene element that is excluded from rendering. As a result of this drawback, users are faced with a complex scene element management problem, requiring additional effort to avoid obvious lapses in realism. The second drawback is that multiple rendering passes are required to render segments into multiple separate frame buffers, thereby requiring additional rendering computation and complexity, and reducing overall efficiency.
As the foregoing illustrates, what is needed in the art is a technique for enabling efficient generation and fine-tuning of high-quality graphics.